Re: [PATCH bpf-next 04/18] bpf: Extend liveness analysis to track stack argument slots

bot+bpf-ci
2026-04-24T18:00:44Z

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> bpf: Extend liveness analysis to track stack argument slots
>
> BPF_REG_PARAMS (R11) is at index MAX_BPF_REG, which is beyond the
> register tracking arrays in const_fold.c and liveness.c. Handle it
> explicitly to avoid out-of-bounds accesses.
>
> In liveness.c, extend the arg tracking dataflow to cover stack arg
> slots. Otherwise, pointers passed through stack args are invisible
> to liveness, causing the pointed-to stack slots to be incorrectly
> poisoned.
>
> Add a parallel tracking array (at_stack_arg_out/at_stack_arg_entry)
> in arg_track_xfer() to record FP-derived values stored to outgoing
> stack arg slots and to restore them on incoming reads. Extend
> record_call_access() to check stack arg slots for FP-derived
> pointers at kfunc call sites, reusing the record_arg_access() helper
> extracted in the previous patch. Pass stack arg state from caller to
> callee in analyze_subprog() so that callees can track pointers
> received through stack args.
>
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>

The commit message describes fixing out-of-bounds accesses and extending
liveness analysis, which suggests this fixes a bug introduced in a prior
commit. Should this include a Fixes: tag? Looking at the commit history, it
appears this should reference:

Fixes: 8ade62ae1543 ("bpf: Support stack arguments for bpf functions")

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